The present invention relates to a method of immunizing a subject against Hepatitis A virus (HAV), and in particular, to such a method in which a vaccine against HAV is administered through the rectal mucosa of the subject.
Infectious diseases are a worldwide cause of morbidity and mortality. Such diseases particularly affect individuals with weaker immune systems, such as children, and are probably the primary worldwide killer of children (The World Health Report 1997, WHO). Travel and other contact between populations have caused the world to become an increasingly mixed environment in terms of the spread of micro-organisms, such as bacteria and viruses, thereby demanding a higher degree of protection for communities from such infectious agents.
The most efficient strategy, which has been proven to be effective in overcoming these major individual and community health problems, is prevention of the disease state by mass vaccination (Review: Vaccine supplement. Nature Medicine, 4:474-534,1998). However, in spite of the great recent progress in the understanding of the immune response and the development of biotechnological tools, the current technology for mass production of vaccines against a broad spectrum of indications is still very costly and in many cases practically unavailable. In addition, even if the vaccines are available, the administration of such vaccines currently requires a needle or other instrument for direct, systemic injection, with very few exceptions. Thus, mass vaccination programs currently require both a large supply of the vaccine, and of the requisite instruments for administering the vaccine, which can render such programs difficult or impossible to perform.
In particular, no mass vaccination program exists for Hepatitis A virus (HAV), a member of the genus Hepatovirus within the viral family picornaviriade. HAV vaccine is currently generated in tissue cultures, which produce a low viral titer, and is therefore expensive. The expense and difficulty of production are such that the HAV vaccine can currently only be purchased for small-scale programs. New modes for cheap and effective mass vaccination are needed. Providing a vaccine through a simple method could significantly increase the number of protected populations.
Recently, a number of investigators have suggested that vaccination against bacterial agents, such as salmonella, or viral agents, such as HIV, may possibly be enhanced through the rectal administration of attenuated or killed bacteria (see for example xe2x80x9cOral and rectal immunization of adult female volunteers with a recombinant attenuated Salmonella typhi vaccine strainxe2x80x9d; Nardelli-Haefliger D, Kraehenbuhl J P, Curtiss R 3rd, Schodel F, Potts A, Kelly S, De Grandi P. Infect Immun. 1996;64:5219-24; and xe2x80x9cA rational basis for mucosal vaccination against HIV infectionxe2x80x9d; Lehner T, Bergmeier L, Wang Y, Tao L, Mitchell E. Immunol Rev. 1999;170:183-96). Rectal, nasal or oral administrations of vaccines have elicited a humoral and in some cases cellular immune response, although such a response has been variable, indicating that vaccines against certain infectious agents may not be successfully administered through one or more of these routes of administration. For some of these vaccines, however, the humoral response generated neutralizing antibodies against the pathogen as proven in the case of the polio oral vaccine developed by Alfred Sabin.
Unfortunately, no such method for administering the HAV vaccine has been successful through a route of administration other than injection. Therefore, the HAV vaccine is currently difficult to administer, such that any mass vaccination program would be expensive and complicated to perform.
There is thus a need for, and it would be useful to have, a method for administering the HAV vaccine through a route other than direct systemic injection.
The present invention is of a method for administering the HAV vaccine to a subject by absorption through a mucosal tissue, particularly through the mucosa of the rectum. The method of the present invention enables the HAV vaccine to be administered to the subject rectally, for example as a suppository or other rectal dosage form, and to successfully immunize the subject against HAV. Thus, the present invention overcomes problems of background art methods of administration, such as systemic administration by injection for example, which require needles, and which are difficult and expensive to perform.
According to the present invention, there is provided a method for administering a viral vaccine to a subject, the viral vaccine being for a virus infecting the subject through a gastrointestinal mucosa, the method comprising the step of: (a) administering the viral vaccine to the gastrointestinal mucosa of the subject.
According to another embodiment of the present invention, there is provided a method for delivering at least one viral encapsidated gene through a gastrointestinal mucosa of a subject, the method comprising the step of: (a) administering the at least one viral encapsidated gene to the gastrointestinal mucosa of the subject.